We propose to better characterize the binocular cooperation which occurs in strabismic subjects with small or large angle esotropic or exotropic deviations, using a battery of clinically popular binocular tests to: 1) determine which tests result in minimum interocular suppression and 2) test the hypothesis that small angle esotropia is, under ideal conditions, associated most frequently with anomalous retinal correspondence (ARC). Also we will study prismatic adaptation, especially in exotropic patients, and the assessment of surgical correction in some of these patients and will examine the relationship between the size of the suppression scotoma and the loss in contrast sensitivity for low spatial frequency targets. We also intend to measure contrast sensitivity (obtained monocularly and binocularly) on all subjects. Strabismic and anisometropic amblyopes display losses in contrast sensitivity with high spatial frequency targets (Hess & Howell, 1977; Levi, Harwerth & Smith, 1979). In addition, strabismic conditions that would be expected to have the largest suppression scotomas appear to be more likely to exhibit low, as well as high, spatial frequency losses in contrast sensitivity (Hess and Howell, 1977). We propose to extend these studies of contrast sensitivity mechanisms in amblyopes to our nonamblyopic strabismics, and to relate the actual measures of the size of suppression scotomas to contrast sensitivity functions obtained in the same subjects. Goals: 1) A better understanding of binocular function in various kinds of strabismus to aid the ophthalmologist and orthoptist in deciding on surgical or prismatic therapy. 2) The design of better stimuli for currently used clinical instruments (e.g., the major amblyoscope) for greater accuracy in assessment. 3) A relationship between the size of binocularly induced suppression scotomas and losses in contrast sensitivity.